Instagram is packed with photos of fitness stars documenting their active lifestyles, uploading photos of their delicious, healthy meals, and showing the results of their hard work, sometimes via shots of their abs. Now, one fitness blogger is demonstrating how much of the defined-ab effect can actually come down to something that's important for everyone, no matter your health or fitness goals: the way you stand.

In a short video, Carly Rowena showed how standing differently changed the appearance of her abs. At certain points in the video, she pushes her stomach out, and at other points, she pulls it in, seemingly engaging her core muscles. There's a big difference in how her stomach looks, which is interesting, and her body-positive message is great: "[Neither look is] more healthy," she writes in the caption. But there’s more to what she’s saying than just looks, and the secret she’s revealing could help you in many ways throughout your day. Check out the video below:

This is a cool effect, but it can be hard enough to remember to keep your abs engaged while exercising. If you're hoping for your abs to look as defined as possible all the time, keeping your core engaged 24/7 can be tough. The good news is that you create a similar effect just by making sure your posture is on point.

It seems silly that something as simple as standing up straight can make it seem like you have more defined or flatter abs, but Jim Pivarnik, Ph.D., a professor of kinesiology at Michigan State University, tells SELF it's completely possible. The mechanism is pretty simple: If you stand up tall and straight, it elongates the muscles and skin so your midsection appears flatter and you can potentially see the muscles more easily; if you slouch, the opposite is true.

Even better, focusing on your posture goes beyond how your midsection looks. Posture is important in fitness because your core muscles' main job is to support your spine during workouts, Albert Matheny, M.S., R.D., C.S.C.S., of SoHo Strength Lab and Promix Nutrition, tells SELF. For example, when you lift weights, your abs stabilize your spine, which helps to prevent injury, he explains.

Good posture can also help you avoid injury when you work out by allowing your muscles to work more effectively, Caitlin Bailey, a professional dancer and senior personal trainer at New York's PhilanthroFIT training studio, tells SELF. "This helps prevent muscle strain, joint pain, and overuse injuries," she says.

Standing up straight is especially important for postpartum women because their abdominal muscles (and therefore posture) have been thrown out of whack by pregnancy, Pivarnik says. Many pregnant women have posture that isn’t great, Matheny says, largely due to weak back and postural muscles that cause them to hunch forward when they carry their baby. “This continues after the baby is born when carrying the baby in their arms,” he says.

To know if your posture needs work, Pivarnik recommends standing in front the mirror in a comfortable position, turning to the side, and seeing how you look. If your shoulders are rounded forward, your head is leaning forward or backward, or your belly is more rounded than you expected, it’s probably time to work on your posture. If your ears are over your shoulders, your rib cage is over your hips, and your hips are over your heels, you likely have good posture, Bailey says. Back pain can also be a sign that you need to stand up straight, Matheny says.

Luckily, there are a few things you can do to improve your posture. Matheny recommends doing exercises to strengthen your posterior chain (the backside of your body), helping you to stand up straighter with ease. Pivarnik says core exercises can also be helpful, as well as ones that target side and back muscles (he recommends trying various types of planks to target these areas). Bailey also suggests trunk twists, which are great for engaging your core while promoting mobility and flexibility. "These can be done with or without a weight," she says.

If you’re not sure where to start or need help for posture-related back pain, Bailey recommends consulting a personal trainer or physical therapist. In the meantime, you can try these six easy moves that will improve your posture.